Interstitial fluid is found in the interstitial spaces of a multicellular animal. It is the main component of extracellular fluid and a source of nutrients for the cells. Interstitial fluid contains glucose, salt, fatty acids, minerals such as calcium, magnesium and potassium, as well as oxygen and other components essential to the survival of cells. Interstitial fluid receives its components via capillaries by means of diffusion.
While significant research effort has been expended regarding the use of interstitial fluid as a biomarker for cancer research and diagnosis, research pertaining to use of interstitial fluid for treatment of disease or damaged tissue appears to be lacking. It has now been found that autologous interstitial fluid can be effectively collected in an implanted accumulation chamber and utilized to provide essential sustenance to preselected target cells at a body site remote from the collection site.
It is well known that fibrous tissue tends to encapsulate implanted devices. This fibrous tissue encapsulation of a foreign body is an attempt to extrude it (“marsupialization”), and occurs primarily with non-porous materials. The body attempts to do the same thing with porous materials, but because the surface area is so large, tissue “in-growth”, rather than extrusion, occurs. Not only does the pore size of the implant material have an influence, but it is also dependent upon the implant location. With pore sizes ranging from 50-250 microns, only fibrous tissue ingrowth is observed; pore sizes smaller than 50 microns are seen as “non-porous” by the body, while pore sizes of greater than 250 microns result in both fibrous tissue and bony ingrowth. There is a limit, however, as to how far into an implanted device tissue will grow. Blood vessels need to be present near the implanted device in order to nourish and stabilize the ingrowing cells. The accepted distance a cell can live away from a capillary is approximately 50 microns.
The present invention provides an efficient sump for collection of interstitial fluid and includes an accumulation chamber which receives the interstitial fluid from surrounding tissue while minimizing undesirable tissue invasion into the accumulation chamber.